This invention relates to the field of synthetic coverings. More particularly, this invention relates to a process for manufacturing synthetic coverings and the products obtained thereby. The process of the present invention is particularly well suited for providing selected areas of distinctive appearance, i.e., matting or graining, on a synthetic covering surface, particularly floor or wall coverings which are based on synthetic materials, usually polyvinyl chloride (PVC). The present invention is related to U.S. patent application Ser. No. 603,843,756 filed on the same day as this application, assigned to the assignee hereof and incorporated herein by reference.
The majority of synthetic plastic coverings do not exhibit a sufficient visual difference between glossy areas and matted or grained areas on the surface thereof. A distinct difference between gloss and mattness is desirable on synthetic coverings in order to provide certain distinctive appearances. For example, certain areas on the surface covering may have a design applied by printing or other means, while other areas may have a joint imitation thereon. This is particularly true when a synthetic covering is intended to imitate a ceramic tile flooring. Accordingly, an important feature for many types of synthetic coverings is that selected areas or zones on the surface thereof have a distinctive visual appearance, especially between glossy areas and matted areas.
In U.S. Pat. No. 4,273,819, matting of the joint between the tiles of a ceramic tile imitation is provided by the addition of a vinyl monomer and a thermal initiator to the entire surface layer followed by hot graining of this surface. The decorative printed areas contain a catalyst which lowers the decomposition temperature of the thermal initiator so that those areas retain a matted (grained) appearance. Conversely, other zones not containing this catalyst will lose their grained appearance during subsequent gelling. The process of U.S. Pat. No. 4,273,819 has certain disadvantages. For example, the process is highly dependent on the graining temperature. Thus, if the temperature is only slightly higher than required, there is a danger of initiating a crosslinking reaction over the entire surface of the synthetic covering and, thereby, achieving an undesirable matted appearance over the entire surface thereof. Conversely, too low a graining temperature will not provide the desired matted appearance even on those portions where the matted appearance is desired, i.e., at the joints. Moreover, in view of the kinetics of the decomposition of the initiator, too long a graining time, even at the correct temperature, presents the same danger as when using too high a graining temperature, i.e., complete graining or matting.
Another prior art technique which is similar to that process described in U.S. Pat. No. 4,273,819 and which also makes it possible to obtain distinctive matted and glossy surface effects is described in FR-A-2,531,009. As in the U.S. Patent, the French Patent suffers from similar deficiencies and drawbacks.